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Rb25 Timing

mbwilding

By mbwilding,
in General Maintenance

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mad082 Grand Master

mad082

Posted
Posted

what do you mean it goes out by 3.5 teeth on every mark? so do you mean that both on the crank and on the cam wheels the timing marks don't line up after you turn the crank 1 rotation? if so, how are you turning the crank?

or do you mean that if you turn the crank 1 turn the cam wheels are 3.5 teeth out but the crank lines up with the timing mark?

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mad082 Grand Master

mad082

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Posted
I think you may be getting confused, this is physically impossible unless the belt is slipping or you have different sized cam gear/crank pulley. The timing belt isn't at a 1:1 ratio as the crank pulley so the timing marks will barely ever line up once you have turned it.

i think i get what you are saying and i think i understand what the OP may have been doing wrong. if he is simply looking at a sticker on the belt and is turning the cranks so that the belt is back to where it was then looking at all 3 timing marks and seeing that they are out then thinking that the timing is out by 3.5 teeth. that made me LOL

other than that, the timing marks on the cam pulleys will ge out after 1 turn of the crank by 180 degrees but after the second turn of the crank they should line up as the crank to cam ratio is 2:1 due to the engine being a 4 stroke and the valves only open on every second rotation of the crank. so as long as every second rotation of the cranks the timing marks all line up then the timing is fine. ignore any marks on the belt.

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blind_elk Grand Master

blind_elk

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Posted

Any marks on the belt itself are irrelevant to setting of the timing. The number of teeth on the belt is not an integer multiple of the number of teeth on the cam wheels, so it is unlikely that those marks on the belt will align with marks on the cam wheels after any number of crank / camshaft revolutions.

The important marks are on the crank pulley and the cam wheels.

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Fry_33 Proficient

Fry_33

Posted
Posted

The marks on the belt are for installation assistance only. Even the arrow is the same thing, timing belts aren't directional but the assistance marks are. That's because the distances between the marks are generally different numbers of teeth. If you are going to take off a belt and reinstall it though install it back so the direction it was moving before is the same.

You can install the belt with the marks on the back (engine) side so you can't even see them if you have the pulley marks lined up with the ones on the block/covers. As most others have pointed out after it's installed ignore the marks on the belt, refer to the pulley/block marks.

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